1. Technical Field of the Invention
The present invention relates to a cylinder head cover including an integrally formed breather apparatus, and to an engine incorporating the cylinder head cover.
2. Background Art
Various cylinder head covers have been proposed in which a breather chamber is formed by a peripheral wall projecting inside of the cylinder head cover, and a breather plate covering an opening of the peripheral wall, where plural ribs are formed extending from the peripheral wall in the breather chamber, thereby setting long maze-like blowby gas flow paths so as to promote gas-liquid separation (see published patent document JP-A 2005-307852, for example).
In the cylinder head cover with built-in breather apparatus as disclosed in published patent document JP-A 2005-307852, a number of breather plate fixing bosses project into inner areas of a breather chamber, and ribs extending from a peripheral wall are continuous with the fixing bosses.
Also in the cylinder head cover with built-in breather apparatus as disclosed in published patent document JP-A 2005-307852, the peripheral wall is made up of a combination of side walls extending in the lateral direction and side walls extending in the front-rear direction. Each of the ribs extends perpendicularly from one of the side walls and reaches one of the fixing bosses.
Further in the cylinder head cover with built-in breather apparatus as disclosed in published patent document JP-A 2005-307852, blowby gas inflow ports are formed in laterally extending front walls. Each of the blowby gas inflow ports is faced by a rib extending perpendicularly from a left or right side wall which extends in the front-rear direction.
In the above breather chamber of published patent document JP-A 2005-307852, the ribs extend from the breather chamber side walls extending in the lateral or front-rear direction with each of the ribs reaching one of the fixing bosses. When, in casting the cylinder head cover that includes the breather chamber, molten metal is poured through a casting gate toward one of the side walls, the molten metal is required to follow a complicatedly bent flow path to flow into one of the thin ribs via two or more of the side walls and reach one of the projecting fixing bosses at the end of the rib. This results in a poor fluidity of the molten metal during manufacture of the cylinder head cover.
Moreover, each of the blowby gas inflow ports is faced by one of the ribs extending perpendicularly from one of the side walls extending in the front-rear direction. Therefore, the blowby gas entering the breather chamber through either of the inflow ports squarely hits the rib facing the inflow port and then advances flowing through between the fixing boss with which the end of the rib is continuous and another one of the side walls. This causes a space behind the rib to be left as an unused dead space. Thus, the breather chamber as a whole is not used as effectively as it could be.